JP6722221B2 - Light emitting diode - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode, and more specifically, a conductive type reflective layer on a p-type semiconductor layer for reflecting light in a short wavelength (UVA wavelength) band of light traveling through the p-type semiconductor layer. And a metal electrode formed on a conductive type semiconductor layer for reflecting light in a short wavelength band and light in a visible light band.

In general, nitrides of group III elements such as gallium nitride (GaN) and aluminum nitride (AlN) have excellent thermal stability and have a direct transition type energy band structure. It has received much attention as a substance for light emitting devices. In particular, blue and green light emitting devices using indium gallium nitride (InGaN) are suitable for various application fields such as large-scale color flat panel display devices, signal lights, indoor lighting, high density light sources, high resolution output systems, and optical communication. It is used.

Since it is difficult to form the same kind of substrate for growing the semiconductor layer of such a group III element nitride semiconductor layer, a metal organic chemical vapor deposition (MOCVD) method is applied to a different kind of substrate having a similar crystal structure. The growth is performed by a process such as a metal organic chemical vapor deposition (MBE) or a molecular beam evaporation (MBE) process. A sapphire substrate having a hexagonal crystal structure is mainly used as the heterogeneous substrate. However, sapphire is an electrically non-conductive material, which limits the structure of the light emitting diode. For this reason, recently, after growing each epitaxial layer such as a nitride semiconductor layer on a heterogeneous growth substrate such as sapphire and bonding a supporting substrate to each grown epitaxial layer, a substrate removal technique such as a laser lift-off technique is used. A technique has been developed for manufacturing a high efficiency light emitting diode having a vertical structure by separating the growth substrate using the growth substrate. In such a vertical structure light emitting diode, an n-type GaN layer, an active layer, and a p-type GaN layer are sequentially formed on a growth substrate, and a p-type ohmic electrode or an ohmic reflective layer is formed on the p-type GaN layer. Then, the sapphire substrate is removed after the supporting substrate is bonded thereon, and the electrode pad is formed on the exposed n-type compound semiconductor layer to manufacture the semiconductor device.

On the other hand, a flip chip type light emitting diode, which has a structure for achieving high brightness and high output and for omitting a bonding wire to the electrode pad side, generally emits light through a sapphire substrate which is not a p type semiconductor layer, The thick p-type electrode can be used to improve the current spreading of the p-type semiconductor layer, and the thermal resistance can be greatly reduced by heat dissipation through the submount substrate.

In the flip chip type light emitting diode and the vertical type light emitting diode, since the light emitted from the active layer to the p type semiconductor layer must be reflected and emitted to the substrate side, the light emitted to the p type semiconductor layer is reflected. In order to reflect light, formation of a reflective layer is an essential element. Generally, the metal electrode serves the function of such a reflective layer.

JP, 2011-192821, A JP, 2016-001740, A

The present invention has been made in view of the above prior art, and an object of the present invention is to provide a light emitting diode using light in a short wavelength (UVA wavelength) band, in which conventional aluminum is used for a reflective layer. An object of the present invention is to provide a light emitting diode that overcomes various disadvantages and improves light extraction efficiency.

Further, an object of the present invention is to have a high reflectance in a wide wavelength region including light in a short wavelength band and to reflect light in a short wavelength band so as to improve light extraction efficiency; Another object of the present invention is to provide a light emitting diode including a second reflection layer that reflects light in the wavelength band and the blue wavelength band.

The light emitting diode according to one aspect of the present invention made to achieve the above object is a first conductive type semiconductor layer having a front surface and a back surface, a second conductive type semiconductor layer having a front surface and a back surface, and the first conductive type. An active layer formed between a back surface of the semiconductor layer and a front surface of the second conductive type semiconductor layer; a second conductive type reflective layer formed on a back surface of the second conductive type semiconductor layer; A reflection part formed on the back surface of the second conductive type reflective layer opposite to the conductive type semiconductor layer and reflecting light in the UVA wavelength band and the blue wavelength band. Includes a plurality of DBR (distributed Bragg reflector) unit layers that reflect light in the UVA wavelength band of 315 nm to 420 nm, and the DBR unit layer is adjacent to the low refractive index layer and the low refractive index layer. includes a high refractive index layer, and the front Symbol reflective portion, a metal reflective layer for reflecting a second conductivity type intermediate layer for improving an ohmic contact, the light of the UVA wavelength band and a blue wavelength band, Of the plurality of DBR unit layers, the second conductivity type impurity doping concentration of the DBR unit layer located closest to the reflection portion is higher than the remaining DBR unit layers.

The thickness of the second conductive type intermediate layer is preferably 10 nm to 150 nm.
The thickness of the second conductive type reflection layer is preferably 60 nm to 1500 nm.
The first conductive type semiconductor layer may be an n type semiconductor layer, and the second conductive type semiconductor layer may be a p type semiconductor layer.
The metal reflective layer may include silver (Ag).
A sapphire substrate may be located on the front surface of the first conductive semiconductor layer.
The semiconductor device may further include a phase-matching layer formed between the second conductive semiconductor layer and the second reflective layer.

The number of DBR unit layer, the reflectance of the second conductivity type reflective layer is preferably adjusted to be 80% or more.

Each of the low refractive index layer and the high refractive index layer may have a thickness of 30 nm to 50 nm.
In the second conductive type reflection layer, three or more of the DBR unit layers are repeated, and the first conductive type DBR unit layers located closest to the back surface of the second conductive type semiconductor layer have the second conductive type impurity doping concentration. It is preferable that a certain first doping concentration is lower than a second doping concentration that is a doping concentration of the remaining DBR unit layers.

A light emitting diode according to another aspect of the present invention made to achieve the above object is a first conductive type semiconductor layer having a front surface and a back surface, a second conductive type semiconductor layer having a front surface and a back surface, and the first conductive type semiconductor layer. An active layer formed between the back surface of the second conductivity type semiconductor layer and the front surface of the second conductivity type semiconductor layer, a second conductivity type reflection layer formed on the back surface of the second conductivity type semiconductor layer, and the second conductivity type semiconductor layer is formed on the back surface of which is opposite said second conductivity type reflective layer reflects light U VA wave length band range and the blue wavelength band, the electrical to the second conductive semiconductor layer manner and a reflecting portion that is connected, the second conductive type reflective layer, a pre-Symbol DBR (distributed Bragg reflector) unit layer for reflecting light 315nm~420nm wavelength band is a U VA wave length band area includes a plurality, of the previous SL plurality of DBR unit layer, a second conductivity type impurity doping concentration of the DBR unit layer located closest to the reflective portion, being higher than the rest of the DBR unit layer.

The DBR unit layer includes a low refractive index layer and a high refractive index layer adjacent to the low refractive index layer, and each of the low refractive index layer and the high refractive index layer has a thickness of 30 nm to 50 nm. Is preferred.
The reflective part is adjacent to the second conductive type reflective layer, has a second conductive type intermediate layer for improving ohmic contact between the second conductive type reflective layer and the reflective part, the UVA wavelength band, and And a metal reflective layer for reflecting light in the blue wavelength band.

The thickness of the second conductive type intermediate layer is preferably 10 nm to 150 nm.
The second conductive type intermediate layer preferably has a thickness of 60 nm to 1500 nm.

According to the present invention, there is provided a light emitting diode including a first reflective layer that reflects a short wavelength (UVA wavelength) band and a second reflective layer that reflects a short wavelength (UVA wavelength) band and a blue wavelength band. , And has a high reflectance in a wide wavelength band including the UVA wavelength band and the blue wavelength band, thereby further improving the light extraction efficiency.

It is a graph which shows the reflectance with respect to the wavelength band of aluminum (Al), gold (Au), and silver (Ag). 1 is a cross-sectional view of a light emitting diode according to an exemplary embodiment of the present invention. 3 is a graph showing a reflectance of a light emitting diode with respect to a wavelength according to an exemplary embodiment of the present invention. In the light emitting diode according to an embodiment of the present invention, a diagram showing an example of the content of aluminum (Al) in the position corresponding to the low refractive index layer and the high refractive index layer of the DBR unit layer constituting the second conductive type reflection layer. is there. In the light emitting diode according to one embodiment of the present invention, another example of the content of aluminum (Al) at the positions corresponding to the low refractive index layer and the high refractive index layer of the DBR unit layer that constitutes the second conductive type reflection layer will be shown. It is a figure. FIG. 3 is a diagram showing various forms of aluminum composition profiles included in a DBR unit layer.

Hereinafter, specific examples of modes for carrying out the present invention will be described in detail with reference to the drawings.

FIG. 1 is a graph showing the reflectance with respect to the wavelength bands of aluminum (Al), gold (Au), and silver (Ag). A metal electrode containing silver (Ag) can be used as the reflective layer. However, in the case of silver, the reflectance is very good (high) in the blue wavelength band, but the reflectance is not good in the UVA wavelength band, which is a wavelength band of approximately 315 nm to 420 nm, as shown in FIG. Therefore, it is difficult to use silver as the reflective layer when implementing a white light emitting diode using light in the UVA wavelength band.

Therefore, aluminum (Al) is used as a reflective layer or an electrode to reflect light in the UVA wavelength band. As shown in FIG. 1, aluminum (Al) has good (high) reflectance in the UVA wavelength band, but the ohmic contact between the p-type semiconductor layer and aluminum is not good, and the aluminum electrode Since a diffusion barrier layer has to be used in order to use, a process for this is required.

2 is a cross-sectional view of a light emitting diode according to an exemplary embodiment of the present invention, FIG. 3 is a graph showing reflectance of a light emitting diode according to an exemplary embodiment of the present invention with respect to wavelength, and FIG. FIG. 6 is a diagram showing an example of the content of aluminum (Al) at positions corresponding to the low refractive index layer and the high refractive index layer of the DBR unit layer that constitutes the second conductive type reflection layer in the light emitting diode according to the embodiment. In the light emitting diode according to the exemplary embodiment of the present invention, reference numeral 5 represents another content of aluminum (Al) at positions corresponding to the low refractive index layer and the high refractive index layer of the DBR unit layer that constitutes the second conductive type reflection layer. FIG. 6 is a diagram showing an example, and FIG. 6 is a diagram showing aluminum composition profiles of various forms included in the DBR unit layer. The light emitting diode shown in each figure is a flip-chip type light emitting diode, and the following description will be focused on this, but the present invention is not limited to the flip chip type light emitting diode, and may be a vertical type light emitting diode. Can be applied as is. Further, in each drawing, the thickness of each layer is exaggerated or schematically shown for convenience of description.

First, a light emitting diode according to an exemplary embodiment of the present invention will be described with reference to FIG. As shown in FIG. 2, the light emitting diode includes a sapphire substrate 10, a first conductivity type semiconductor layer 20, an active layer 30, a second conductivity type semiconductor layer 40, a second conductivity type reflection layer 50, a first electrode 80, and a second electrode. The reflection part (72, 74) as an electrode and the phase matching layer 90 are included.

The first conductive type semiconductor layer 20 and the second conductive type semiconductor layer 40 have a front surface and a back surface, respectively. In FIG. 2, the first conductivity type semiconductor layer 20 is an n-type semiconductor layer, and the second conductivity type semiconductor layer 40 is a p-type semiconductor layer. The front surface of each of the first conductive type semiconductor layer 20, the second conductive type semiconductor layer 40, and the second conductive type reflective layer 50 is the surface facing upward in FIG. 2, and the back surface is the lower surface in FIG. Shows the side facing.

The active layer 30 is formed between the back surface of the first conductive type semiconductor layer 20 and the front surface of the second conductive type semiconductor layer 40. The active layer 30 is a layer in which light is generated by recombination of electrons and holes, and is formed in a multiple quantum well (MQW) structure. For example, the active layer 30 is composed of a nitride semiconductor layer such as InGaN, AlGaN, AlGaInN, or GaN.

The first conductive type semiconductor layer 20, the active layer 30, and the second conductive type semiconductor layer 40 are formed by chemical vapor deposition (CVD), metal organic chemical vapor deposition (MOCVD), plasma chemical vapor deposition. (PECVD: plasma-enhanced chemical vapor deposition), molecular beam epitaxy (MBE), hydride vapor phase epitaxy (HVPE: hybrid vapor phase epitaxy) and the like.

The first electrode 80 is a component electrically connected to the first conductive type semiconductor layer 20, and the reflective portion 72, 74 is formed on the back surface of the second conductive type reflective layer 50. The second conductive type intermediate layer 72 serves to function as two electrodes and improves ohmic contact, and a metal reflection layer 74 for reflecting light in the UVA wavelength band and the blue wavelength band. For example, the first electrode 80 is an electrode electrically connected to the n-type semiconductor layer 20, and the reflection part (72, 74) functions as a second electrode electrically connected to the p-type semiconductor layer 40. To do. The metal reflective layer 74 of the reflective portion functions as the second reflective layer when the second conductive type reflective layer 50 described below functions as the first reflective layer. The thickness of the second conductivity type intermediate layer 72 is approximately 10 nm to 150 nm.

The second conductive type reflective layer 50 is formed on the back surface of the second conductive type semiconductor layer 40, that is, between the back surface of the second conductive type semiconductor layer 40 and the reflective portion (72, 74), and is formed from the active layer. The light in the short wavelength band emitted through the second conductive type semiconductor layer 40 is reflected. Here, the short wavelength band corresponds to the UVA wavelength band and has a wavelength of approximately 315 nm to 420 nm.

The second conductive type reflection layer 50 includes a plurality of DBR unit layers (50a, 50b, 50c,..., 50z). Hereinafter, one of the DBR unit layers (50a, 50b, 50c,..., 50z), which is representative of 50a, will be described as an example. The DBR unit layer 50a includes a low-refractive index layer 50a1 and a high-refractive index layer 50a2 adjacent to the low-refractive index layer 50a1, and the low-refractive index layer 50a1 is formed of Al _x Ga _1-x N (0<x≦1. ) wherein the high refractive index layer 50a2 _{includes Al y Ga 1-y N (} 0 ≦ y <1, y <x). The number of DBR unit layers (50a, 50b, 50c,..., 50z) included in the second conductive type reflection layer 50 is variable. The number of DBR unit layers is adjusted so that the reflectance of the second conductive type reflection layer 50 is approximately 80% or more. As used in the description of the low refractive index layer 50a1 and the high refractive index layer 50a2, the term "adjacent" means that the layers are directly adjacent to each other without intervening other components, or in a state where other components are intervening. Means adjacent to each other.

As shown in FIG. 2, when the second conductive type reflection layer 50 includes a plurality of DBR unit layers (50a, 50b, 50c,..., 50z), the low refractive index layer 50a1 and the high refractive index layer 50a2 are The pattern will be repeated continuously and alternately.

For example, when the second conductive type semiconductor layer 40 is a p-type semiconductor layer, the second conductive type reflective layer 50 is a p-type DBR. The low-refractive index layer 50a1 and the high-refractive index layer 50a2 are Al _x Ga _1-x N (0<x≦1) and Al _y Ga _1-y N (0≦y<1, y, respectively) as described above. <x), but since the refractive index of AlN is lower than the refractive index of GaN (about 2.4 in the UV band), the low refractive index layer 50a1 always has a higher Al content than the high refractive index layer 50a2. Is included higher.

In the general formula of the low refractive index layer 50a1 and a high refractive index layer 50a2, a low refractive index layer 50a1 is _Al x _{Ga 1-x} N, the high refractive index layer 50a2 is _{Al y Ga 1-y} N. Here, the relational expression between x and y is 0≦y<x≦1. That is, the content of aluminum (Al) in the low refractive index layer 50a1 is higher than the content of aluminum (Al) in the high refractive index layer 50a2. Further, the compositions of the low refractive index layer 50a1 and the high refractive index layer 50a2 are changed stepwise so that the rapid change of the energy band can be reduced. Describing based on the above formula, for example, the low refractive index layer 50a1 is made of AlN, and the high refractive index layer 50a2 is made of GaN.

As shown in FIG. 2, when the second conductive type reflection layer 50 includes a plurality of DBR unit layers (50a, 50b, 50c,..., 50z), a plurality of DBR unit layers (50a, 50b, 50c,. , 50z), the second conductivity type impurity doping concentration of the DBR unit layer 50z located closest to the reflection part (72, 74) serving as the second electrode is higher than the remaining DBR unit layers. As a result, ohmic contact with the reflection part (72, 74) which becomes the second electrode can be improved. For example, when the second conductivity type impurity is a p-type impurity, the last DBR unit layer 50z located closest to the reflection part (72, 74) serving as the p-type electrode is increased to a maximum of 5×10 ²⁰ cm ^−3. It is formed of a heavily doped p-type semiconductor layer.

In the DBR unit layers (50a, 50b, 50c,..., 50z) of the second conductive type reflection layer 50, the first three DBR unit layers (50a, 50b, 50a, 50b, which are located closest to the back surface of the second conductive type semiconductor layer 40). The first doping concentration, which is the second conductivity type impurity doping concentration of 50c), is lower than the second doping concentration that is the second conductivity type impurity doping concentration of the remaining DBR unit layers. This is because the free carrier absorption of the DBR unit layer, which is located closer to the active layer 30 than the rest of the second conductive type reflection layer 50, is relatively large. This is to reduce this. The second doping concentration is the doping concentration of the remaining DBR unit layer in the second conductive type reflection layer 50. For example, the second doping concentration is approximately 1×10 ¹⁸ cm ⁻³ to 1×10 ²¹ cm ^−3, which is the second conductivity type impurity doping concentration of the first three DBR unit layers (50a, 50b, 50c). The certain first doping concentration is approximately 1×10 ¹⁶ cm ^{−3 to} 5×10 ¹⁷ cm ⁻³ . The total thickness of the second conductive type reflection layer 50 is, for example, approximately 60 nm to 1500 nm, and the thickness of the DBR unit layer (for example, 50a) is approximately 60 nm to 100 nm. In the DBR unit layer (for example, 50a), the low refractive index layer 50a1 and the high refractive index layer 50a2 each have a thickness of approximately 30 nm to 50 nm.

The phase matching layer 90 is added between the second conductive type semiconductor layer 40 and the second conductive type reflective layer 50, and is a layer for maximizing the effective reflectance. As with the first three DBR unit layers (50a, 50b, 50c), the second conductivity type impurity doping concentration of the phase matching layer 90 is set to the second conductivity type impurity doping concentration to reduce free carrier absorption. 2 Lower than the doping concentration. For example, the second doping concentration is approximately 1×10 ¹⁸ cm ⁻³ to 1×10 ²¹ cm ⁻³ , and the second conductivity type impurity doping concentration of the first three DBR unit layers (50a, 50b, 50c) and All the second impurity doping concentrations of the phase matching layer are 1×10 ¹⁶ cm ^{−3 to} 5×10 ¹⁷ cm ⁻³ . For example, the phase matching layer 90 _{includes Al x Ga 1-x N (} 0 <x <1), thickness is 5 nm to 50 nm.

As described above, according to the present invention, the second conductive type reflection layer 50 that functions as the first reflection layer that reflects the UVA wavelength band and the metal reflection layer that functions as the second reflection layer that reflects the UVA wavelength band and the blue wavelength band. 74, the light emitting diode according to the present invention has a high reflectance in a wide wavelength band including the UVA wavelength band and further improves the light extraction efficiency. Further, by reflecting the light propagating in the direction of the p-type semiconductor layer and adding a conductive type DBR to improve the light efficiency, a current path is formed when an existing non-conductive type DBR is formed. It has an advantage that the additional process of can be reduced.

Next, referring to FIG. 3 showing the reflectance with respect to the wavelength of the light emitting diode according to the embodiment of the present invention shown in FIG. 2, referring to FIG. S1) and below) are wavelength bands (defined as UVB and UVC) that are not used to implement white light emitting diodes, and Section 2 is a part of the UVA wavelength band (315 nm to 420 nm). 2 is mainly reflected by the second conductive type reflection layer 50 in FIG. In Section 2, as indicated by the solid line in the figure, the second-conductivity-type reflective layer 50 exhibits a reflectance of 90% (0.9) or more in this wavelength band. Then, the section 3 is a part of the UVA wavelength band and a blue wavelength band, and the reflection of this part is reflected by the metal reflection layer 74, as shown by the broken line in the figure. The broken line in the figure shows the case where silver is used as the metal reflective layer 74. Therefore, in the present embodiment, the second conductive type reflection layer 50 that functions as the first reflection layer that reflects the UVA wavelength band, and the metal reflection layer 74 that functions as the second reflection layer that reflects the UVA wavelength band and the blue wavelength band. By providing the light emitting diode including and, the light extraction efficiency is further improved by having a high reflectance in a wide wavelength band including the UVA wavelength band.

In the light emitting diode according to the exemplary embodiment of the present invention described with reference to FIG. 2, the low refractive index layer 50a1 of the DBR unit layer (for example, 50a) may include Al _x Ga _1-x N (0<x≦1). wherein, the high refractive index layer 50a2 is explained _the case of including the _{Al y Ga 1-y N (} 0 ≦ y <1, y <x). Correspondingly, the content of aluminum (Al) in the second conductive type reflection layer 50 will be described with reference to the drawings. Each of these examples is shown in FIGS. In each figure, the x-axis shows the position of the second conductive type reflection layer 50, and the y-axis shows the Al content. Here, the position along the vertical direction of the second conductive type reflection layer 50 shown in FIG. 2 corresponds to the x axis.

First, referring to FIG. 4, a is a low refractive index layer 50a1, b is a high refractive index layer 50a2, and a+b is a DBR unit layer 50a. As described above, since the low refractive index layer 50a1 has the highest Al content, the low refractive index layer 50a1 is substantially an AlN layer. Since the high refractive index layer 50a2 has the lowest Al content, the high refractive index layer 50a2 is substantially a GaN layer. Therefore, in this case, the second conductive type reflection layer 50 has a pattern in which the AlN layers and the GaN layers are alternately repeated.

Next, referring to FIG. 5, a is a low refractive index layer 50a1 and b is a high refractive index layer 50a2. In this example, the DBR unit layer 50a includes a first transition part t1 having a gradually lower Al content between the low refractive index layer 50a1 and the high refractive index layer 50a2, and includes the high refractive index layer 50a2 and the next DBR layer 50a2. The unit layer (50b in FIG. 1) includes a second transition part t2 having a gradually increasing content with the low refractive index layer 50a1. In the case of FIG. 5, 0.5t2+a+0.5t1 is a low refractive index layer, 0.5t1+b+0.5t2 is a high refractive index layer, and a+b+t1+t2 is the total thickness of one DBR unit layer. Considering the relationship with the wavelength, the optical thickness of one DBR unit layer, that is, a+b+t1+t2 is designed to be λ/2. Further, the thickness of each of the low refractive index layer 50a1 and the high refractive index layer 50a2 is designed to be λ/4 in one DBR unit layer. The Al content profile of the first transition part t1 and the second transition part t2 may have various forms, for example, a linear or quadratic curve form.

Referring to FIG. 6, a start point P3 and an end point P4 of the first transition part t1, and a start point P1 and an end point P2 of the second transition part t2, that is, respective dissimilar junction points (P1, P2, P3, P4). ) Is a point where the Al content does not change gradually but changes rapidly, and delta doping is performed only at this point to reduce the rapid change in the energy band. In the present specification, the description of the profile of each figure is based on the content of Al, but the DBR unit layer includes Al _x Ga _1-x N (0<x≦1) and Al. Since it consists of _y Ga _1-y N (0≦y<1, y<x), the Ga content also changes correspondingly.

In general, delta doping is a method of doping with a profile such as a delta function, and when background doping is increased in the doping process of the second conductive type reflective layer 50, free carrier absorption is reduced. In order to prevent this, the second doping concentration is set to a level of 1×10 ¹⁸ cm ⁻³ to 1×10 ²¹ cm ⁻³ and the content of Al changes in order to prevent this. By applying such delta doping only to a portion, that is, each transition portion (t1, t2), abrupt changes in energy band caused by changes in Al content are reduced, and the second conductive type reflection layer 50 is formed. Reduce the resistance at.

As described above, the present invention provides a light emitting diode having a new concept, and thus silver or silver for forming a current path is provided as compared with the case of forming a non-conductive DBR on a conventional p-type semiconductor layer. Not only does it need to use metal reflective electrodes that do not have good mechanical/electrical contact performance with p-type semiconductor layers such as aluminum, but it also significantly improves light efficiency without the use of additional metal reflective layers. Can be made.

The embodiments of the present invention have been described in detail above with reference to the drawings. However, the present invention is not limited to the above-described embodiments, and various modifications are made without departing from the technical scope of the present invention. It is possible to carry out.

10 Sapphire substrate 20 1st conductivity type semiconductor layer 30 Active layer 40 2nd conductivity type semiconductor layer 50 2nd conductivity type reflective layer 50a, 50b, 50c,..., 50z DBR unit layer 50a1 Low refractive index layer 50a2 High refractive index layer 72 Second conductive type intermediate layer (of reflection part) 74 Metal reflection layer (of reflection part) 80 First electrode 90 Phase matching layer

Claims (15)

A first conductivity type semiconductor layer having a front surface and a back surface;
A second conductivity type semiconductor layer having a front surface and a back surface;
An active layer formed between a back surface of the first conductive type semiconductor layer and a front surface of the second conductive type semiconductor layer;
A second conductive type reflective layer formed on the back surface of the second conductive type semiconductor layer;
A reflector formed on the back surface of the second conductive type reflection layer opposite to the second conductive type semiconductor layer, for reflecting light in the UVA wavelength band and the blue wavelength band,
The second conductive type reflection layer,
The DBR unit layer includes a plurality of DBR (distributed Bragg reflector) unit layers that reflect light in the UVA wavelength band of 315 nm to 420 nm, and the DBR unit layer has a low refractive index layer and a high refractive index adjacent to the low refractive index layer. Including a stratum ,
The reflector is
A second conductive type intermediate layer for improving ohmic contact;
A metal reflective layer for reflecting light in the UVA wavelength band and the blue wavelength band,
Among the plurality of DBR unit layers, the second conductivity type impurity doping concentration of the DBR unit layer located closest to the reflection part is higher than that of the remaining DBR unit layers. The light emitting diode according to claim 1, wherein the second conductive type intermediate layer has a thickness of 10 nm to 150 nm. The light emitting diode of claim 1, wherein the second conductive type reflection layer has a thickness of 60 nm to 1500 nm. The light emitting diode of claim 1, wherein the first conductive type semiconductor layer is an n type semiconductor layer and the second conductive type semiconductor layer is a p type semiconductor layer. The light emitting diode according to claim 1, wherein the metal reflective layer includes silver (Ag). The light emitting diode of claim 1, wherein a sapphire substrate is located on the front surface of the first conductive semiconductor layer. The light emitting diode of claim 1, further comprising a phase-matching layer formed between the second conductive type semiconductor layer and the second conductive type reflective layer. The light emitting diode of claim 1, wherein the number of the DBR unit layers is adjusted such that the reflectance of the second conductive type reflection layer is 80% or more. The light emitting diode according to claim 1, wherein each of the low refractive index layer and the high refractive index layer has a thickness of 30 nm to 50 nm. In the second conductive type reflection layer, three or more of the DBR unit layers are repeated, and the first conductive type DBR unit layers located closest to the back surface of the second conductive type semiconductor layer have the second conductive type impurity doping concentration. The light emitting diode of claim 1, wherein a certain first doping concentration is lower than a second doping concentration that is a doping concentration of the remaining DBR unit layer. A first conductivity type semiconductor layer having a front surface and a back surface;
A second conductivity type semiconductor layer having a front surface and a back surface;
An active layer formed between a back surface of the first conductive type semiconductor layer and a front surface of the second conductive type semiconductor layer;
A second conductive type reflective layer formed on the back surface of the second conductive type semiconductor layer;
The second conductive type semiconductor layer is formed on a back surface of the second conductive type reflective layer opposite to the second conductive type semiconductor layer, reflects light in a UVA wavelength band and a blue wavelength band, and is electrically connected to the second conductive type semiconductor layer. And a reflector connected to
The second conductive type reflection layer,
A plurality of DBR (distributed Bragg reflector) unit layers that reflect light in the UVA wavelength band of 315 nm to 420 nm,
Among the plurality of DBR unit layers, the second conductivity type impurity doping concentration of the DBR unit layer located closest to the reflection part is higher than that of the remaining DBR unit layers. The DBR unit layer includes a low refractive index layer and a high refractive index layer adjacent to the low refractive index layer,
The light emitting diode according to claim 11, wherein each of the low refractive index layer and the high refractive index layer has a thickness of 30 nm to 50 nm. The reflector is
A second conductive type intermediate layer adjacent to the second conductive type reflective layer for improving ohmic contact between the second conductive type reflective layer and the reflective portion;
The light emitting diode according to claim 11, further comprising a metal reflection layer for reflecting light in the UVA wavelength band and the blue wavelength band. The light emitting diode of claim 13, wherein the second conductive type intermediate layer has a thickness of 10 nm to 150 nm. The light emitting diode according to claim 11, wherein the second conductive type reflection layer has a thickness of 60 nm to 1500 nm.

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